Disordered polymer antireflective coating for improved perovskite photovoltaics

Light management through low index medium, such as antireflective coating (ARC) provides practical solution to improve the efficiency of photovoltaics. However, a brute-force development of photonic structure on ARC is not necessarily useful, because of random scattering associated with impediment of light transmission. Here, we leverage the concept of disorder, rather than random, structured on ARC for improving efficiency without modifying original architecture of thin-film photovoltaics. We demonstrate a disordered polymer that leads to a total reflectance of 5% while demonstrating a high transmission of 94% across 300 to 820 nm wavelength. Next, we find that the arrangement of disordered points and line arrays constructing the polymer seems to be the key to control bandwidth performance of the ARC. Finally, we apply this into Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3 perovskite, and through experiments with wave-optics and full-device simulation, show a 1.6-fold absorption gain leading to 19.59% power-conversion-efficiency by the disordered ARC.Ministry of Education (MOE)National Research Foundation (NRF)Accepted versionThis work is supported by the National Research Foundation, Prime Minister’s Office, Singapore under Energy Research Innovation Program (Grant number, NRF2015EWT-EIRP003-004 and NRF-CRP14-2014-03 and Solar CRP:S18-1176-SCRP), and Ministry of Education (MOE2016‐T2‐1‐052)

Printable low-temperature carbon for highly efficient and stable mesoscopic perovskite solar cells

Carbon-based perovskite solar cells (C-PSCs) have attracted worldwide attention in the research community due to their low-cost fabrication and improved stability compared with conventional PSCs. However, the cell reproducibility and inconsistency of perovskite infiltration into micrometer-thick mesoscopic devices remain an issue for cell fabrication. Furthermore, full perovskite crystallization in the screen-printed device without any perovskite formed on the mesoporous carbon electrode is always challenging. The presence of protruding perovskite crystals on C-PSCs is found, which initially leads to the hydrolysis of perovskites under humid condition and eventually accelerates the degradation. Herein, a low-temperature (low-T) carbon layer is incorporated through a scalable screen-printing technique on top of C-PSCs. C-PSCs coated with low-T carbon show good moisture (70% relative humidity) and thermal (65 and 85 °C) stability over 3,250 and 1,000 h, respectively, without any physical encapsulation. The device also shows high stability under continuous illumination at its maximum power point for 175 h. This hydrophobic and conductive carbon layer not only protects the exposed perovskite crystals from moisture but also enhances the photovoltaic performance of C-PSCs with major fill factor and open-circuit voltage improvement.Ministry of Education (MOE)National Research Foundation (NRF)The authors would like to acknowledge funding from the Singapore National Research Foundation through the Intra-CREATE Collaborative Grant (NRF2018-ITC001-001) and MOE Tier 2 project MOE2019-T2-2-097